This invention was made with Government support under Contract No. DE-FC21-95MC31176 awarded by the Department of Energy. The Government has certain rights in this invention.
The present invention relates to seals for sealing adjacent components in a gas turbine and particularly relates to an overlapping interference seal for minimizing fluid flow through a gap between adjacent components and methods of assembly.
Many and various types of seals have been applied between adjacent components to seal the components to one another or to minimize the flow between opposite sides of the seal. For example, spline seals are employed to prevent or minimize leakage through the gap between adjacent shroud segments of a gas turbine. It will be appreciated that a plurality of such shroud segments are arranged in an annular array thereof about the rotor axis of a gas turbine. Both of the inner and outer side walls of the shrouds form a gap between high and low pressure regions which either must be sealed or at least leakage flow minimized. Such spline seal systems utilize long narrow flat seals loosely assembled in opposing slots of two adjacent side walls of the shrouds. The pressure differential forces the spline seal against a sealing surface along each of the shroud slots. The slots and spline seal serve to create two labyrinth paths, impeding leakage flow through the gap. While such spline seals have been satisfactory, they are characterized by high temperatures, variable pressure gradients and excessive life requirements. Thus, there is a need for a seal between components in a gas turbine having improved sealing characteristics.
In accordance with a preferred embodiment of the present invention, there is provided an overlapping interference seal for sealing a gap between a pair of adjacent gas turbine components. The seal is rugged and robust and can tolerate finite amounts of relative motion, misalignment and manufacturing tolerances. To accomplish the foregoing, and in a first embodiment hereof, there is provided a pair of gas turbine components, for example, shrouds, disposed in side-by-side relation one with the other with a gap therebetween. The components generally have planar surfaces along the edges of the components adjacent the gap. A seal element is disposed between the components and has seal surfaces engaging the planar surfaces of the components. The seal element is secured to one of the components and overlies a planar sealing surface along the opposite component, enabling relative sliding movement therebetween. Because the seal element is formed of a thin material, the high pressure on one side of the seal element forces the element into contact and sealing engagement along the planar surface of the other component to effect the seal. In this embodiment, the seal element includes an upturned elongated leading edge. With the proximal edge of the seal secured to one of the components, the assembly of the seal is facilitated by displacing the components toward one another. In this manner, the leading upturned edge of the seal element engages along the opposing surface of the component, enabling a smooth engagement of the sealing element with the planar surface. The sealing element may be employed separately from or in combination with a spline seal. The spline seal may be disposed in slots along the adjoining edges of the components, with the sealing element overlying the spline seal.
In another form of the present invention, a pair of sealing elements are provided. One sealing element is fixed to one of the components and has an elongated leading edge, while the other sealing element is fixed to the other component. A recess is formed in the components for receiving a spline seal. The recess may directly underlie the sealing elements or comprise registering slots along opposing side edges of the components to receive the spline seal. One of the edges of the recesses is preferably chamfered to facilitate assembly of the seal, as described below. In final assembly, the one sealing element overlies the other sealing element, forming a seal between their contacting surfaces. The underlying sealing element may also overlie and contact a portion of the spline seal between the components. Alternatively, the spline seal may be spaced from the sealing elements and have chamfered surfaces along opposite edges thereof to facilitate assembly of the seal.
The present invention also embraces a method of forming the seal. For example, the adjacent components are placed in lateral registration with one another. As the components are relatively advanced toward one another, the leading edge of the sealing element facilitates initial engagement between the sealing element and the other component. Continued displacement causes the sealing surface to engage along the planar surface. Where two sealing elements are employed, the spline seal is first inserted into the recess, e.g., slot. In one form, the spline seal is inserted between a component and one of the sealing elements and is releasably retained, e.g., clamped between the component and element. Consequently, with a chamfer on the other component and a leading edge on the other sealing element, the components may be displaced toward one another with the sealing element and spline engaging between the first sealing element and the component with the chamfer. Alternatively, the spline seals may have chamfers along opposite edges to facilitate their insertion into the recess, e.g., slots, upon relative displacement of the components toward one another.
In a preferred embodiment according to the present invention, there is provided in a gas turbine, a seal between high and low pressure regions, comprising a pair of members spaced from one another and movable toward and away from one another, each member having a generally planar surface, a seal element between the members and having sealing surfaces engaging the planar surfaces, respectively, the seal element being secured to one of the members, one of the sealing surfaces of the seal element being in slidable engagement with the planar surface of another of the members and the seal element having a leading edge overlying another member and extending away from another member.
In a further preferred embodiment according to the present invention, there is provided in a gas turbine, a seal between high and low pressure regions, comprising first and second members spaced from one another and movable toward and away from one another, each member having a generally planar surface, first and second seal elements carried by the first and second members, respectively, the seal elements having respective sealing surfaces in slidable engagement with one another, one of the seal elements having a leading edge overlying another of the sealing elements and extending away from another sealing element, each member having an elongated recess in opposition to an elongated recess along an opposing member, an elongated spline seal engaged in the recesses and having sealing surfaces therealong engaging seal faces along the recesses of the members, the spline seal extending between the members and lying on one side of the seal element.
In a further preferred embodiment according to the present invention, there is provided in a gas turbine having first and second members spaced from one another and movable toward and away from one another, a seal including at least one sealing element between the members, the sealing element being fixed to the first member and extending therefrom to overlie a planar sealing surface along the second member, a method of assembling the seal, comprising the steps of forming a leading edge on one sealing element along a distal edge thereof extending to one side of a plane containing the sealing element and displacing at least one of the members toward another member such that the leading edge guides the one sealing element along the second member to engage a sealing surface carried by the one sealing element along an opposite side of the plane containing the sealing element against the planar sealing surface of the second member to form a seal between the members.
In a further preferred embodiment according to the present invention, there is provided in a gas turbine having first and second members spaced from one another and movable toward and away from one another, a seal between the members including first and second sealing elements carried by the first and second members, respectively, a method of assembling the seal comprising the steps of forming a leading edge on the first sealing element along a distal edge thereof extending to one side of a plane containing the first sealing element and displacing at least one of the members toward another of the members such that the leading edge guides the first sealing element along the second sealing element to engage a sealing surface carried by the first sealing element along an opposite side of the plane against a sealing surface carried by the second sealing element.